(a) Field of the Invention
The present invention relates to an abnormal operation prevention circuit for a display device and a method for operating the same and, more particularly, to an abnormal operation prevention circuit that prevents pixels of a display element from being deteriorated in display characteristics.
(b) Description of the Related Art
FIG. 1 is a block diagram illustrating the structure of a usual display device.
As shown in FIG. 1, the display device 20 includes a display unit 100 with a plurality of pixels, a driving unit 300 for controlling operation of the respective pixels of the display unit 100, and a power control unit 200 for supplying a power to the display unit 100 and the driving unit 300 while controlling the power. The display unit 100 may be a liquid crystal display, a plasma display panel, or a cathode ray tube.
In case a thin film transistor liquid crystal display (TFT-LCD) is used as the display unit 100, signals Vsync for identifying frames of picture data, signals Hsync for identifying line units, signals DE for identifying data output sections, standard clock signals, and data signals (signals per pixels of red, green and blue) are applied to the display device 20 from a signal source 10 of PC or TV.
The respective signals applied to the display device 20 are processed at the driving unit 300, and transformed into signals for driving the respective pixels in a direct manner. In the TFT-LCD, the signals are applied to the TFTs in the form of a gate driving pulse array and a source driving pulse array. The power control unit 200 generates gate driving voltages, common voltages or gray scale voltages, and supplies the voltages to the relevant units.
In the normal operation of the display device, the pixels do not bear problems such as degradation in display characteristics and image sticking. However, in case the input signals of DE, Vsync or Hsync are intercepted under the continuous supply of power from the power control unit (referred to hereinafter simply as the xe2x80x9cabnormal operationxe2x80x9d), such problems become serious.
In such an abnormal operation, the output voltage from the driving unit is not controlled so that gate or source driving voltages may be applied to the pixels for a long time, or extremely high voltages may be applied thereto. Consequently, ion impurities in the liquid crystal within the pixel area tend to be absorbed into a polyimide film while making abnormal electric potential charge, and this causes image sticking.
Other display devices such as a plasma display panel and a cathode ray tube also involve the same problems. Therefore, it is a critical factor in improving the performance characteristics of the display device to prevent such an abnormal operation. For instance, in a cathode ray tube, phosphors may be deteriorated due to landing of electron beams for a long period of time. In a plasma display panel, such light emission elements may be deteriorated due to plasma discharge within a cell for a long period of time.
In this respect, a pixel protection circuit is used to identify whether the signal of Vsync or Hsync from the signal source is intercepted, and if necessary, to stop the supply of power or to replace such a signal with another control signal within the driving unit. Such a protection circuit currently available is made as ASIC, and attached to the display device, or incorporated into a control IC of the driving unit. This makes it necessary to re-design other relevant control circuits, resulting in increased production cost.
It is an object of the present invention to provide a display device which has a circuit for preventing the abnormal operation in a simplified manner.
This and other objects may be achieved by a display device with the following features.
The display device includes a display unit with a plurality of pixels for displaying picture images, a driving unit for controlling operation of the respective pixels of the display unit, a power control unit for supplying a power to the driving unit and the display unit while controlling the power, and an abnormal operation prevention circuit for preventing the pixels from being deteriorated in display characteristics due to interception of an input signal into the driving unit when the power is continuously supplied to the driving unit from the power control unit.
The abnormal operation prevention unit includes a signal sampling unit connected to an input terminal of the driving unit to receive the input signal into the driving unit in parallel without incurring variation in the input signal, a filtering unit connected to an output terminal of the signal sampling unit to receive the output signal from the signal sampling unit, and a transmission unit connected to an output terminal of the filtering unit to receive the output signal from the filtering unit. The filtering unit filters high frequency portions of the received signal by way of a predetermined constant number to output the signal portions of a predetermined pulse width or more to a transmission unit while intercepting the signal portions of less than the predetermined pulse width. The transmission unit transforms the received signal into an input signal for intercepting power supply from the power control unit or intercepting application of an abnormal signal to the pixels from the driving unit.
The signal sampling unit is provided with a circuit for reverse-turning the input signal into the driving unit.
The filtering unit is formed with a passive and/or active filter having one or more resistors and one or more capacitors. The filter filters high frequency portions of the received signal by way of a predetermined constant number to output the signal portions of a predetermined pulse width or more while intercepting the signal portions of less than the predetermined pulse width.
The transmission unit may be provided with a circuit for reverse-turning the output signal from the filtering unit in case a reverse-turned pulse signal is used as the input signal for intercepting power supply from the power control unit or intercepting application of an abnormal signal to the pixels from the driving unit.
In a method for preventing abnormal operation of the display device, the abnormal operation prevention circuit first receives the input signal into the driving unit in parallel without incurring variation in the input signal at the abnormal operation prevention circuit. Second, high frequency portions of the received signal are filtered by way of a predetermined constant number to output the signal portions of a predetermined pulse width or more while intercepting the signal portions of less than the predetermined pulse width. Third, the filtered output signal is transformed into an input signal for intercepting power supply from the power control unit or intercepting application of an abnormal signal to the pixels from the driving unit.
The input signal into the driving unit is reverse-turned at the first step.
The output signal at the second step may be reverse-turned at the third step in case a reverse-turned pulse signal is used as the input signal for intercepting power supply from the power control unit or intercepting application of an abnormal signal to the pixels from the driving unit.
The display unit may be a liquid crystal display, a plasma display panel, or a cathode ray tube.